Modern wireless networks apply various techniques for conveying information and voice signals between a base station and multiple mobile phones (also referred to a mobile stations). These techniques include Time Division Multiplex Access (TDMA), Frequency Division Multiplex Access (FDMA) and Code Division Multiple Access (CDMA). Some wireless networks such as GSM networks utilize more than a single technique.
A single base station can exchange signals with multiple mobile phones. These mobile phones can be positioned at different distances from the base station. Accordingly, different mobile phones can be associated with different signal propagation periods. In order to compensate for timing differences resulting from the different propagation periods the base station determines, for each mobile phone, a timing advance value. The timing advance value changes in a relatively slow manner, especially in relation to the small timing differences between adjacent transmission bursts.
The following U.S. patents and patent applications, all being incorporated herein by reference, provide a brief overview of prior art timing advance methods and systems: U.S. Pat. No. 6,210,819 of Luders; U.S. Pat. No. 6,804,212 of Vallstrom et al.; U.S. patent application 2005/0053099 of Spear et al.; U.S. patent application 2004/0151143 of Abdesselem et al.; U.S. patent application 2004/0128095 of Oestreich; U.S. patent application 2003/0117995 of Koehn et al.; U.S. patent application 2003/0119524 of Carlsson; U.S. patent application 2004/0203921 of Bromhead et al.; U.S. patent application 2004/0246923 of Achard and U.S. patent application 2005/0025095 of Kim.
Modern mobile phones include multiple integrated circuits (also referred to as ICs or chips). A typical GSM transceiver includes a base band integrated circuit (BBIC) and a Radio Frequency integrated circuit (RFIC). The BBIC and the RFIC exchange control signals and data signals via a digital interface. Various companies, including Agere Systems, Philips, Silicon Laboratories, Sony, Renesas, Motorola, RF Micro Devices, Infineon and TTPcom defined a standardized interface known as DigRF. The DigRF includes a receive and transmit data line, various control lines, and a reference clock line.
The RFIC includes a reception path and a transmission path. The transmission path includes a fractional-N synthesizer, tunable amplifiers, various filters and modulators that can perform amplitude modulation and/or phase modulation. A modern cellular phone may be able to perform GMSK and 8PSK modulation. GMSK includes phase modulation only while 8PSK includes phase and amplitude modulation. In GMSK modulation each symbol is equivalent to one bit while in 8PSK modulation each symbol is equivalent to three bits.
The RFIC shapes the transmission bursts according to predefined power V time masks. The shaping is implemented by controlling the gain of a variable gain power amplifier that is located in the cellular phone front end. Typical power masks are defined in the following technical specification: ESTI TS 145 005 V. 5.9.0, titled “Digital cellular telecommunication system (Phase 2+); Radio transmission and reception (4GPP TS 45.005 version 5.9.0. Release 5), which is incorporated herein by reference.
3GPP defines five types of transmission bursts as part of the EGPRS and GSM standard: normal burst, frequency correction burst, synchronization burst, dummy burst and access bursts. Each burst is characterized by its overall length, its active length and its useful length. The active and useful lengths are shorter than the overall length.
The active length of the normal burst, frequency correction burst, synchronization burst and the dummy burst is one hundred and forty eight symbols. These symbols are followed by eight and a quarter guard period symbols. The access burst is much shorter. Its active length is eighty eight symbols. These symbols are followed by up to sixty eight and one quarter guard period symbols. During the guard period between the first transmission burst to another the mobile phone can perform a power ramp down and a power ramp up.
A (E)GPRS capable cellular phone can transmit a sequence of transmission bursts. The cellular phone has to guarantee that the transmission bursts are transmitted without overlaps and within the allocated time slot for the cellular phone. This goal is achieved by the BBIC that executes a complex and resource consuming transmission control scheme. The BBIC has a processor and additional circuitry that generate interrupts to the processor when certain transmission related events have to be triggered. This scheme is not effective as the BBIC has to handle many tasks and the frequency of interrupts decrease its performance.
There is a need to provide an efficient method and device for transmitting a sequence of transmission bursts without Base band intervention.